/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.naming.factory;

import org.apache.naming.ResourceLinkRef;
import org.apache.naming.StringManager;

import javax.naming.*;
import javax.naming.spi.ObjectFactory;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * <p>Object factory for resource links.</p>
 *
 * @author Remy Maucherat
 */
public class ResourceLinkFactory implements ObjectFactory {

	// ------------------------------------------------------- Static Variables

	private static final StringManager sm = StringManager.getManager(ResourceLinkFactory.class);

	/**
	 * Global naming context.
	 */
	private static Context globalContext = null;

	private static Map<ClassLoader, Map<String, String>> globalResourceRegistrations =
			new ConcurrentHashMap<ClassLoader, Map<String, String>>();

	// --------------------------------------------------------- Public Methods

	/**
	 * Set the global context (note: can only be used once).
	 *
	 * @param newGlobalContext new global context value
	 */
	public static void setGlobalContext(Context newGlobalContext) {
		SecurityManager sm = System.getSecurityManager();
		if (sm != null) {
			sm.checkPermission(new RuntimePermission(
					ResourceLinkFactory.class.getName() + ".setGlobalContext"));
		}
		globalContext = newGlobalContext;
	}

	public static void registerGlobalResourceAccess(Context globalContext, String localName,
	                                                String globalName) {
		validateGlobalContext(globalContext);
		ClassLoader cl = Thread.currentThread().getContextClassLoader();
		Map<String, String> registrations = globalResourceRegistrations.get(cl);
		if (registrations == null) {
			// Web application initialization is single threaded so this is
			// safe.
			registrations = new HashMap<String, String>();
			globalResourceRegistrations.put(cl, registrations);
		}
		registrations.put(localName, globalName);
	}

	public static void deregisterGlobalResourceAccess(Context globalContext, String localName) {
		validateGlobalContext(globalContext);
		ClassLoader cl = Thread.currentThread().getContextClassLoader();
		Map<String, String> registrations = globalResourceRegistrations.get(cl);
		if (registrations != null) {
			registrations.remove(localName);
		}
	}

	public static void deregisterGlobalResourceAccess(Context globalContext) {
		validateGlobalContext(globalContext);
		ClassLoader cl = Thread.currentThread().getContextClassLoader();
		globalResourceRegistrations.remove(cl);
	}

	private static void validateGlobalContext(Context globalContext) {
		if (ResourceLinkFactory.globalContext != null &&
				ResourceLinkFactory.globalContext != globalContext) {
			throw new SecurityException("Caller provided invalid global context");
		}
	}

	private static boolean validateGlobalResourceAccess(String globalName) {
		ClassLoader cl = Thread.currentThread().getContextClassLoader();
		while (cl != null) {
			Map<String, String> registrations = globalResourceRegistrations.get(cl);
			if (registrations != null && registrations.containsValue(globalName)) {
				return true;
			}
			cl = cl.getParent();
		}
		return false;
	}


	// -------------------------------------------------- ObjectFactory Methods

	/**
	 * Create a new DataSource instance.
	 *
	 * @param obj The reference object describing the DataSource
	 */
	@Override
	public Object getObjectInstance(Object obj, Name name, Context nameCtx,
	                                Hashtable<?, ?> environment) throws NamingException {

		if (!(obj instanceof ResourceLinkRef)) {
			return null;
		}

		// Can we process this request?
		Reference ref = (Reference) obj;

		// Read the global ref addr
		String globalName = null;
		RefAddr refAddr = ref.get(ResourceLinkRef.GLOBALNAME);
		if (refAddr != null) {
			globalName = refAddr.getContent().toString();
			// Confirm that the current web application is currently configured
			// to access the specified global resource
			if (!validateGlobalResourceAccess(globalName)) {
				return null;
			}
			Object result = null;
			result = globalContext.lookup(globalName);
			// Check the expected type
			String expectedClassName = ref.getClassName();
			if (expectedClassName == null) {
				throw new IllegalArgumentException(
						sm.getString("resourceLinkFactory.nullType", name, globalName));
			}
			try {
				Class<?> expectedClazz = Class.forName(
						expectedClassName, true, Thread.currentThread().getContextClassLoader());
				if (!expectedClazz.isAssignableFrom(result.getClass())) {
					throw new IllegalArgumentException(sm.getString("resourceLinkFactory.wrongType",
							name, globalName, expectedClassName, result.getClass().getName()));
				}
			} catch (ClassNotFoundException e) {
				throw new IllegalArgumentException(sm.getString("resourceLinkFactory.unknownType",
						name, globalName, expectedClassName), e);
			}
			return result;
		}

		return null;
	}
}
